1. Field of the Invention
The present invention relates to an ink-jet recording apparatus. In particular, the present invention relates to an ink-jet recording apparatus in which nozzles for discharging inks of a plurality of colors are arranged or aligned so that the influence of heat exerted by a driving circuit is inconspicuous.
2. Description of the Related Art
As disclosed in Japanese Patent Application Laid- open Nos. 2002-240306 (FIGS. 4 and 6) corresponding to U.S. Pat. Nos. 6,679,595 and 2003-80793 (FIGS. 6, 9, and 14) corresponding to U.S. Patent Application Publication No. 2003/0063449 A1, an ink-jet recording apparatus is known, in which inks are discharged from a recording head to perform the recording on a recording medium. The recording head includes a plurality of nozzles which are arranged in arrays, a cavity plate which has a plurality of pressure chambers and which is formed to have a substantially rectangular stacked structure, and a piezoelectric actuator plate which is adhered to and stacked on the cavity plate. A flexible wiring board (wiring member), which is electrically connected to respective piezoelectric actuators provided for the piezoelectric actuator plate, is superimposed and stacked on the piezoelectric actuator plate. An IC chip (driving circuit), which outputs the driving signal for discharging the inks from the nozzles, is arranged on the flexible wiring board.
The recording head is divided into two pieces. The flexible wiring board is connected to each of the two recording head pieces. The IC chip is arranged on each of the flexible wiring boards. The two flexible wiring boards extend in an identical direction and in the direction of arrangement of the nozzles which are arranged in arrays.
In the case of the conventional ink-jet recording apparatus, the respective nozzle arrays, which correspond to the inks of the plurality of colors, are disposed at equal distances from the IC chip, because the flexible wiring board extends in the direction of extension of the nozzle arrays. When the IC chip generates the heat as the recording head is driven, the nozzles for the respective colors are affected equivalently by the heat of the IC chip. The discharge characteristic of the ink to be discharged from the nozzles is changed depending on whether the temperature is low or high. In the case of the pale or light color such as the yellow ink, the disturbance is inconspicuous even when the landing position and/or the dot size is disturbed on the recording medium. However, in the case of the deep or dark color, for example, in the case of the black ink, the disturbance is conspicuous. Therefore, the disturbance appears as the deterioration of the recording quality.
In the case of the ink-jet recording apparatus as described above, the lateral width of the flexible wiring board is disposed in a direction substantially perpendicular to the direction of arrangement of the nozzles, which is narrow. For this reason, when the number of nozzles is increased in order to realize a high quality of the recording on the recording medium, the following problem has arisen. That is, the number of wirings formed along the lateral width of the flexible wiring board is further increased, and the wiring density is raised. The wirings are formed extremely finely. The production becomes difficult, and the production cost becomes expensive.
Further, in the case of the ink-jet recording apparatus as described above, the difference in the distance from the IC chip is increased at the both ends of the nozzle arrays for every respective inks. Therefore, the following problem has arisen. That is, the signals, which are inputted from the IC chip into the respective piezoelectric actuators, are affected by the wiring resistance on the flexible wiring board. The discharge characteristics of the inks are changed at the both ends of the nozzle arrays, and the recording quality on the recording medium is deteriorated.
In view of the above, the inventors have proposed the following structure as disclosed in U.S. Pat. No. 6,715,862 and United States Patent Application Publication No. 2004/0125177 in order to widen the lateral width of the flexible wiring board. That is, the flexible wiring board is extended in the direction substantially perpendicular to the direction of arrangement of the nozzles, and the IC chip is arranged in the vicinity of the recording head. In such a structure, the difference is decreased in the distance from the IC chip to the both ends of the nozzle arrays, and the influence of the wiring resistance of the flexible wiring board is decreased. However, a problem has arisen such that the recording is disturbed, and the recording quality is deteriorated.